1 heat 2 thickness charpy

Date 06-11-2007 17:18

What code are you working to? Most codes are material specific and not thickness specific with Charpy's so chances are one test on that material will qual all thicknesses anyway. In fact, double check your code, often you don't even have to do Charpy's for materials under 5/8".

By hogan

Date 06-11-2007 17:41

it's a DOT spec for the 3/8". they do not address the issue on the charpy thickness, just that it be 15ft lb @ 40.

By js55

Date 06-11-2007 17:59

I'm not familiar with DOT specs, some in here may be. But generally the Charpy test is imposed based upon materials and is not limited by thickness. It sounds as though this applies in this case as well. Though you may want to verify the 3/8" threshold. The reason I say this is that there is a fundamental change in fracture mechanism at ~the 5/8" thickness, so many specs only require Charpy's at > 5/8" T.
If you find you have to run em I would run the test on the 1/2" material. That way by the time your lab gets done machining you can still use the standard 3/8" Charpy specimen.
You should have no trouble with 15 ft/lbs @ 40deg F.

By js55

Date 06-11-2007 18:19

Another point, keep in mind that most Charpy tests are weld metal tests. Sometimes HAZ, and sometimes a comparison of BM to HAZ. So most likely you will be testing the weld metal and not the BM.
You need to read the spec carefully and determine which is the case.
The only problem I can possibly foresee would be dilution of Vanadium and Columbium from the BM into the weld metal (more a problem toward the root pass). But I truly doubt that the requirement will still prove problematic.

By hogan

Date 06-11-2007 19:35

it's just the base metal. these specs are a little different than typical. i'm also required to get charpys on my shapes.

By waynekoe (**)

Date 06-11-2007 19:52

If you contact the mill, they maybe can perform the CVN there, rather than you having to go to all the hassel. The project I'm on now had that same spec requirement (also DOT). They originally wanted a CVN for "each A500 HSS tube (thats each piece for each brace) to be used in construction. It was finally agreed upon to have it done by/at the mill, in sections. You might give it a try?

By js55

Date 06-11-2007 19:52

If its just BM and not related to a PQR you may be able to get data from the manufacturer off the MTR. If its not on the one you have it may be cheaper to ask for it with Charpy's than to do your own test. If the test temp is equal to or lower than your required 40, as long as you hit the 15 ft/lbs you're good.

By CHGuilford (****)

Date 06-12-2007 16:34

Check out ASTYM A673 Section 5.

Assumning you require "H" frequency, I would test the 1/2" plate and you will be OK for the 3/8" (Assuming the test passes, of course. It is rare but once in a while they don't pass. But A673 explains re-tests also.)

By hogan

Date 06-12-2007 18:49

thanks for the astm, but i believe that after reading the first paragraph my customer would not accept it. they do like to be critical of everything

By CHGuilford (****)

Date 06-13-2007 16:30

Understood. Been there. Just an FYI, you should NOT have to pay $375 for a CVN test ($100 per specimen) and a charge for reduced temperatures. There are other labs that are much cheaper. We were paying $80 for a CVN test of 3 specimens done at any (reasonable) temperature; I believe that is still the rate.